(1) Field of the Invention
The present invention relates to gear systems, and more particularly to backlash eliminators in gear arrangements.
(2) Prior Art
Gear apparatus are used to drive rolls mounted for rotary motion in an embossing or engraving machine to emboss a web traveling between the rolls. The longitudinal and circumferential alignment of such rolls during the embossing process is of utmost importance. When the machine is in operation any circumferential motion between the rolls will sometimes result in a mutilated transfer of pattern to the material between the rolls. Changing gears is required on the roll assembly to remove backlash and maintain alignment when the gap between the rolls, and hence the center distance between gears, is varied even if only a fraction of an inch. Rotation or readjustment of the gears is required when the gear train is reversed.
Helical or herringbone gears are the best way to attempt circumferential alignment. These are shown in U.S. Pat. Nos. 3,512,477 to Nelson; 3,793,899 to Bourbonnaud; 3,803,936 to Kroeper; and 3,545,296 to Eggins. The alignment, that is, the reduction or elimination of backlash, is not always maintained, especially when the rolls and hence, the gears are separated to allow for various widths of webs traveling therebetween. As the gears become separated, the teeth become partially disengaged and meshing contact at the pitch line between the separate gears becomes impossible. When this occurs, backlash may be evidenced.
The patent to Geiger, U.S. Pat. No. 3,636,789 shows a gear drive utilized to move gun turrets, wherein the gear drive has a double pinion shaft which is axially displacable by means of a pressure medium to cause helical gears to pressurizably engage counter gears. The gear drive shown in the Geiger Patent operates only on fixed centers, and as such would not eliminate backlash operating on a set of rolls having a web traveling therebetween.
The patent to Eggins, U.S. Pat. No. 3,545,296 shows a variable gear tooth assembly having an arrangement of split pinions movable relative to one another to change the effective loading of a respective pinion as compensation for irregularities in a large gear. The gear tooth assembly is not adapted to variable centers between the axes of the two gear shafts, and it uses spacers or the like to keep the split pinions apart as opposed to letting the pinions react fully with its associated gear engaged therewith.
The patent to Wright, U.S. Pat. No. 1,435,571 shows a gearing arrangement wherein a pair of helical gears are axially displacable with respect to one another and are biased apart to cause circumferential displacement of their contiguous teeth to cause a diminished intertooth spacing, making the teeth of an engaging gear fill the intertooth space completely to reduce noise and wear. This gearing arrangement is used for single direction rotation only, and is not adaptable here for variable center distance systems.
Thus, it is an object of the present invention to provide a gear system which eliminates backlash for its gearing arrangement regardless of the direction of rotation of the gears.
It is a further object of the present invention to provide a gear system utilizable with a roll arrangement, to permit indexing therebetween.
It is yet a further object of the invention to provide a gear system which will eliminate backlash therewithin, while also permitting the distance between centers of axes of cooperating gears to be changed as necessary.